Rust-proofing composite solutions

ABSTRACT

RUST-PROOFING AQUEOUS OR ALCOHOLIC COMPOSITE SOLUTIONS FOR APPLICATION TO METAL SURFACES CONSISTING ESSENTIALLY OF AN AMINE SALT OF A FATTY ACID, AN ALKALI METAL SALT OF BENZOIC ACID AND AN ALKANOLAMIDE.

Uited States Patent Q 3,573,225 RUST-PROOFING COMPOSITE SOLUTIONSMasahiko Kondo, 3-14-7 Maechi, Saitama Prefecture, Urawa, Japan, andTetsuo Shinmura, 27 Futaba-cho, Itabashi-ku, Tokyo, Japan No Drawing.Filed Feb. 1, 1968, Ser. No. 702,209 Int. Cl. C23f 11/14, 11/10 US. Cl.252-392 6 Claims ABSTRACT OF THE DISCLOSURE Rust-proofing aqueous oralcoholic composite solutions for application to metal surfacesconsisting essentially of an amine salt of a fatty acid, an alkali metalsalt of ben- Zoic acid and an alkanolamide.

This invention relates generally to rust-proofing compositions forapplication to metal surfaces and has particular reference to suchaqueous or alcoholic composit solutions which consist essentially of anamine salt of a fatty acid, an alkali metal salt of benzoic acid and analkanolamide.

There are known a variety of rust preventives useful for protectingmetal surfaces against corrosion attack, most widely used of which is anoil-film forming material. This material also varies in kind, andalthough some are better than the others in terms of the length of timein which they retain rust-proofing efficacy, they are all adequate forall practical purposes.

However, these unctuous rust preventives are difficult to remove fromthe metal surfaces to which they have been applied. This film removaloperation is time-consuming and troublesome, requiring the use of analkali solution or chlorinated solvents such as trichloroethylene andperchloroethylene with which to wash the film otf sometimes withheating, or sometimes using petroleum series solvents.

To eliminate such difficulty, there have more recently been introducedcertain water-soluble rust-proofing com positions which need not beremoved after deposit on the metal surfaces or may be removed with ease.Typical examples are an alkali metal nitrite, dicyclohexylammoniumnitrite, cyclohexylammonium nitrite and an alkali metal chromate. Theseaqueous solutions have been found useful insofar as the metal is soakedtherein, but they are not quite as effective as oil counterparts whenapplied to the metal surfaces and exposed to the outside atmosphere forextended periods of time.

It is the primary object of the present invention to provide new, usefulrust-proofing or rust-preventive compositions of this character whichhave prolonged efficacy in protecting metal surfaces against corrosionand which can be removed therefrom with utmost ease as the occasioncalls for.

It is another object of the invention to provide rustproofingcompositions which, on application to metal surfaces, will form atransparent or translucent uniform film thereby retaining the originalsurface appearance of the metal.

.Briefiy stated, the inventive concept of the present invention residesin the peculiar combination of an amine salt of a fatty acid, an alkalimetal benzoate and an alkanolamide whereby there is obtained a highlyeffective, long-lasting rust preventive product. It has been empiricallyascertained that the absence of any one of the three compounds or anyone thereof alone cannot achieve the desired characteristics of the rustpreventives comparable to, or better than existing oil typecounterparts.

An amine salt of a fatty acid having a certain range of molecular weightis known as a volatile rust preventive 3,573,225 Patented Mar. 30, 1971compound which tends to sublimate at room temperature.

An alkali metal benzoate is known as a contact rust preventive compounduseful for coating on metal surfaces, and it may be added with acorrosive solution to make the most of its rust-preventive tendency.

An alkanolamide has both surface-active and contact rust-preventiveproperties. This surface-active agent helps reduce the surface tensionof the composite solution when applied to metal surfaces, so that thecontact rust-preventive tendency of the solution is so much increased.

It has been discovered that an amine salt of a fatty acid, e.g.cyclohexylamine laurate, and an alkali metal bonzoate, e.g. sodiumbenzoate, are highly conducive to the rust-preventive life time, whilean alkanolamide co-present in the composite solution serves to reducethe surface tension thereof, so as to facilitate its deposit on metalsurfaces. Experiments show that the rust-proofing composite solutionaccording to the invention will form on the metal surface a uniform filmabout 0.005 to 5 microns thick after the water or alcoholic contentsthereof have evaporated.

There are different theories to account for the mechanism in whichorganic corrosion-inhibitors exhibit their rust-proofing activity onmetal surfaces. One theory is based on the physical adsorption of theinhibitor to the metal surface. Another theory is based on the chemicaladsorption. Still another theory attributes it to the formation of achelate compound.

With an organic corrosion-inhibitor dissolved in water, alcohol orbenzene, for application to metal surfaces, it would be useless, were itnot for a deposit of adequate amounts of the inhibitor on the metalsurfaces, even if there has been formed a chelate compound which wouldnecessarily be only appreciable and susceptible to destruction byambient causes.

On the other hand the alkanolamide included in the compositerust-preventive composition according to the present invention has apeculiar surface-active effect to permit the amine salt of a fatty acidand the alkali metal benzoate to deposit on metal surfaces in an amountgreater than required for chemical adsorption, although it does notpossess as great corrosion-inhibitive activity as the latter twocompounds.

Experiments revealed that the best results are obtainable by blending50l00 parts by weight of amine salt of fatty acid, 20-200 parts ofalkali metal benzoate, and 1-50 parts of alkanolamide to 0.520%consistency in an aqueous or alcoholic solution. Blends in excess of theupper limit of this range were found commercially unfeasible, and thoseless than the lower limit inoperative. More specific blendingproportions will be discussed in the examples given hereinafter.

The term, amine salt of fatty acid according to the invention includesreaction products of a saturated fatty acid having a carbon number of618 with an alkylor cycloalkyl-amine having a carbon number of 6-12, forexample, cyclohexylamine laurate, dicyclohexylamine caprylate,cyclohexylamine myristate and octylamine stearate. The saturated fattyacid and the amine are reacted in a mol ratio equivalent to each other,or with a slight excess of the latter, the resulting product being inthe form of a salt free of amide bonds.

The term alkali metal benzoate includes sodium benzoate, potassiumbenzoate and lithium benzoate. Instead of the alkali metal benzoate,nitrite compounds such as sodium nitrite may be used.

The term alkanolamide includes reaction products of a fatty acid havinga carbon number of 618 with N-hydroxyethyl or N,Nbis-hydroxyethylcapramide, N-hydroxyethyl or N,N-bis-l1ydroxyethyl oleamide; orN-hydroxyethyl or N,N-bis-hydroxyethyl lauramide. 1 mol of such fattyacid is reacted with 2 mols of the alkanolamide, so that the excess ofthe latter loosely combines with the resulting amide thereby affordingenhanced water-solubility.

The rust-preventive compositions according to the invention may beapplied to iron, alloys thereof, alumi- 4 purposes of comparison. Eachpacked test piece was placed in a 60 C., 90% relative humidity constanttemperature container and disposed thus for 15 consecutive days, withthe results given in Table l.

5 num, tin, zinc, and other metals. This may be done by the EXAMPLE 2use of brush, rolls, sprayers, or otherwise by dipping the metal in thecomposite of the invention. Three gltlerent sample solutlon? prepared amanner similar to Example 1, using d1cyclohexylam1ne EXAMPLE 1caprylate, N-hydroxyethyl oleamide and sodium benzoate. There wereprepared three difierent aqueous solutions: Water methanol were used asscilvelltkThe samitest the first was a composite aqueous solution ofcyclohexylm Extmple 1 was treatFd m 3 cmdltlons amine laurate N,N bishydmxyethyl lauramide} and to1 0 tam onh 1ts surface 0 6 micron thlckfilm of the sodium benzoate; the second was a composite aqueous EacPacked test Plece 0 dlsposefl for days solution of any two of the abovethree compounds; and 15 m q fi temperatllvre col'llallief Cychng every16 the third was a mono aqueous solution of any one of the 2 2 l 2 of E60 and 80% l f above three compounds, as tabulated below um it an everyours with another set of cond1t1ons of 5 C. and 80% relative humidity.Commercially available oil-type counterparts similarly participated inthis 20 test. Test results are shown in Table 2. I

TABLE 1 Corrosioninhibitive TABLE 2 Amounts factor Compounds by weight(percent) Corrosion- Arnounts inhibitive 1( DIyIsIIcaliezrgliliminelaurlalte "a... 10% C d lily factorisy roxyet 1y aurami e. 1 ompoun sWei 1; ercent) Sample Sodium benzoate. 100 100 g p Water 1. 3,000Dieyclohexylamlne caprylate- 100 Cyclohexylamine laurat 150N-hydroxyethyl oleamide... 20 N,N-bis-hydroxyethyl laura 60 75 581111310Sodium benzoate 100 100 Water a, 000 1,500 S 1 Cyclohe aur 150 1,500 amp9 Sodium heuzoate 60 90 200 ater 3,000 N-hydroxyethyl oleamide 20 N,N-bis-hydroxycthyl laurarm e.. 150 Water 1,500 Sodium benzoata 60 9sample 2 Methanol 1, 500 Water 3,000 Dicyclohexylamine eapry1ate 110Cyclohexylarninelaura e 210 so Sodlum benzoate 110 85 Water. "Kart i 3,000 xlgtitgnnl 1, 580 N,N-bisoxyethyl auranu e 210 1 6 am 1,5 0 Sample\vateruui 3,000 i 70 Dicyclohexylamine enprylate. 220

Sodium benzoate 210 85 Water 1,500 60 Water 3, 000 Methan 1, 500Conventional oil type rust preventives 95 s 1 3 N-hydroxyethyl o1eamlde220 Untreated steal 20 40 amp 6 Water 1,500 40 Methanol- 1, 500Note.Corrosi0n-inhibitive factor is represented by rust-free surfaceS0d1l1mbe11Z0flt6- 220 area/test piece surface area X 100. Water 1, 50075 Methan 1,500 Conventional oil type rust preventives. 80 Untreatedsteel 5 NoTn-Corrosionduhibitiye factor is represented by rust- A testpiece of cold-roll steel measuring mm. x free Surface e e p e s face aea x100. mm. X 1.2 mm. was immersed in each sample solution andimmediately taken out for exposure to the atmosphere EXAMPLE 3 for about30 minutes, until a film of this solution about 0.7 micron thick wasformed on the surfaces of the test 50 Example 2 was followed, except forthe use of pure piece. The test piece thus treated was packed in a.polyaluminum measuring 60 mm, x 8 mm. x 2 mm. as a test ethylenelaminated paper but unsealed to permit aeration. piece. Corrosion of thetest piece was determined by Commercially available rust preventives ofthe oil type comparing the surface condition of the test piece prioralso participated in this test under similar conditions, for totreatment with that after treatment.

TABLE 3 Amounts Y Compounds weight Surface condition Dicyclohexylamlneeapry1ate N-hydroxyethyl eloamide 20 sample Sodium benzoate 100Unchanged. Water 1,500 Methanol- 1, 500 Dicyclohexylamme caprylate. 200N -hydroxyethyl oleamide 20 w 1,500

1,500 sampie Dicyclohexylamme eaprylate 11 Partly whlm spot rust Sodiumbcnzoate Water 1,500 Methanol 1, 500 Dieyclohexylamlne caprylate 220Water 1,500 Methanol 1, 500 N-hydroxyethyl oleamlde.-. 220 Sample Water1, 500 Partly white spot rust.

Methanol 1,500 Sodium benzoate 220 We 1,500 M 1,500

Untreated aluminium White rust in total surface.

EXAMPLE 4 The various sample solutions listed in Table 4 below wereprepared, 100 cc. of each of which were placed in a container measuring9 cm. in inside diameter and cm. in height. A test piece of cold-rollsteel measuring 6 cm. x 10 cm. x 0.2 cm. was introduced halfway into thecontainer, and disposed thus for 30 consecutive days, with the upperhalf portions of the test piece exposed to the atmosphere. A blank testwas also conducted with use of distilled water.

a fatty acid selected from the group consisting of the reaction productsof amines having 6l2 carbon atoms and a saturated fatty acid having 618carbon atoms, 20O parts by weight of an alkali metal benzoate, 1-50parts by weight of an alkanolamide selected from the group consistingthe reaction products of ethanolamines and a saturated fatty acid having6-18 carbon atoms, and a mixture of alcohol and water in an amount toproduce an 0.520% alcohol solution.

5. A rust-proofing composite solution as claimed in claim 4, wherein thealkali metal benzoate is selected Distilled waterNOTE.-Corrosion-inhibitive factor is represented by rusttree surfacearea/test piece surface area X100.

What is claimed is:

1. A rust-proofing composite solution consisting essentially of 50-100parts by weight of an amine salt of a fatty acid selected from the groupconsisting of the reaction products of amines having 6-12 carbon atomsand a saturated fatty acid having 6-18 carbon atoms, 20-200 parts byweight of an alkali metal benzoate, 1-50 parts by weight of analkanolamide selected from the group consisting of the reaction productsof ethanolamines and a saturated fatty acid having 6-18 carbon atoms,and water in an amount to produce an 05-20% aqueous solution.

2. A rust-proofing composite solution as claimed in claim 1, wherein thealkali metal benzoate is selected from the group consisting of sodiumbenzoate, potassium benzoate and lithium benzoate.

3. A rust-proofing composite solution as claimed in claim 2, wherein theamine salt of a fatty acid is selected from the group consisting ofcyclohexylamine laurate, dicyclohexylamine caprylate, cyclohexylarninemyristate and octylamine stearate, and said alkanolamide is selectedfrom the group consisting of N-hydroxyethyl olearnide,N,N-bis-hydroxyethyl capramide and N,N-bishydroxyethyl lauramide.

4. A rust-proofing composite solution consisting essentially of 50-100parts by weight of an amine salt of References Cited UNITED STATESPATENTS 2,739,870 3/1956 Senkus 252392 2,782,164 2/1957 Fischer et al.252-392 2,850,461 9/1958 Bloch et al. 252-394 RICHARD D. LOVERING,Primary Examiner I. GLUCK, Assistant Examiner U.S. Cl. X.R.

